The present invention relates to a magnetic head arrangement for use in recording and reproducing signals, and more particularly, to a magnetic head arrangement including a thin layer.
The technology of employing a thin layer for a magnetic head has greatly improved the accuracy of positioning the magnetic head and has made it possible to form the magnetic head compact in size, and eventually, has opened a new field for the magnetic head. One of the most outstanding features of this thin layer type magnetic head is that it is possible to align a plurality of magnetic head units on one substrate along a direction perpendicular to a plane of, and to the direction of movement of, a recording medium, such as, a magnetic tape or disc, and within the width of the recording medium to form a multitrack type magnetic head arrangement. When compared with the conventional magnetic head arrangement formed by a bulky material, more than ten times the number of magnetic head units can be formed.
Although there is the advantage mentioned above, the magnetic head arrangement formed by a thin layer has problems to be solved, one of which is to improve the density of magnetic force produced from each of the heads to a degree sufficient to record the tape without causing any interferences between the neighboring tracks aligned densely. For this purpose, the size of the winding of each magnetic head should be not larger than the width of the corresponding track. Since the thin layer type magnetic head has a plane structure, an increase of the number of the windings results in an increase of the area occupied by the magnetic head. Therefore, the number of windings is limited to a certain number and, therefore, it is difficult to increase the number of windings. To produce a sufficient magnetic field, the current fed through the coil is increased. Although, the pattern of the coil winding, maybe a multilayer pattern or a zig-zag pattern, such patterns are not appropriate from the view point of the size they occupy and the manufacturing process they require. Therefore, it is preferable to employ a spiral pattern for the coil winding. The spiral winding not only is simple in construction but also is reliable in operation.
FIGS. 1(a) and 1(b) show a prior art multitrack type magnetic head arrangement formed by a thin layer, in which FIG. 1(a) is a top plan view of the magnetic head arrangement and FIG. 1(b) is a cross-sectional view taken along a line I(b)-I(b) shown in FIG. 1(a). The prior art magnetic head arrangement includes a plurality of magnetic head units 9 aligned with a predetermined pitch P along a direction perpendicular or orthogonal to the direction of advance of the recording medium, each unit 9 having a spiral coil 4 formed by a thin layer of electrically conductive material. The spiral coil 4 is supported on an electrically insulating layer 2 deposited on a substrate 1 made of magnetic material, and has a center opening which is referred to as a window 3. The magnetic head unit 9 further has a strip of magnetic layer 8 which has a contacting portion 8a, intermediate portion 8b and a gap forming portion 8c. The contacting portion 8a is located within the window 3 for establishing a magnetic connection between the substrate 1 and the contacting portion 8a. For this purpose, a portion of the insulating layer 2 located in the window 3 of the coil 4 should preferably be removed to improve the magnetic connection between the contacting portion 8a and the substrate 1. The gap forming portion 8c is located adjacent to an edge 1a of the substrate 1 for forming a predetermined gap G at a position adjacent to a recording medium T. The intermediate portion 8b is positioned between the contacting portion 8a and gap forming portion 8c. In order to prevent any electrical connection between the windings of the spiral coil 4, a suitable insulating layer of filler is provided between the coil 4 and the magnetic layer 8. When an electrical current is fed through the spiral coil 4, it generates magnetic flux, as shown by dotted lines, that runs through a closed loop formed by magnetic layer 8, gap G and the substrate 1 for impressing a magnetic signal on the recording medium T by the magnetic flux that leak outwardly from the gap G towards the recording medium T.
According to the prior art magnetic head arrangement described above, the magnetic layer 8 has a width W1 approximately equal to the width W0 of the window 3 along its entire length. Accordingly, a ratio (W1/P) of the width W1 particularly at the gap forming portion 8c to the pitch P is very small, resulting in low percentage of utilization of the recording medium T. To overcome such a disadvantage, one may attempt to widen the width of the gap forming portion 8c to W2 as shown in FIG. 2. However, according to this structure, there occurs a disadvantage that the density of the magnetic flux, which is highest at an intermediate portion 8b adjacent to the contacting portion 8a, becomes low towards the gap forming portion 8c, resulting in low magnetic flux produced across the gap G, i.e., in low core efficiency.
Furthermore, according to the prior art magnetic head arrangement described above, the magnetic flux at the intermediate portion 8b adjacent to the contacting portion 8a may saturate, resulting in an insufficient transmission of magnetic motive forced produced by the current flowing through the spiral coil 4.
Moreover, according to the prior art magnetic head arrangement described above, some percentage of magnetic flux generated by the current flowing through the inner winding of the spiral coil 4 may leak out from the magnetic layer 8, so that the magnetic flux produced across the gap G will become low.